Don't modify memory access right when changing data in debug stub.

tests/gdb/nacl.scons

Index: tests/gdb/nacl.scons
===================================================================
--- tests/gdb/nacl.scons	(revision 9621)
+++ tests/gdb/nacl.scons	(working copy)
@@ -68,6 +68,15 @@
 env.AddNodeToTestSuite(node, ['large_tests'],
                        'run_gdb_step_from_func_start_test')
 
+node = env.CommandTest(
+    'gdb_call_from_gdb.out',
+    command=['${PYTHON}', env.File('call_from_gdb.py')],
+    osenv=env_vars + ['GDB_TEST_GUEST=%s' % gdb_test_guest.abspath],
+    extra_deps=[sel_ldr, irt, gdb_test_guest])
+
+env.AddNodeToTestSuite(node, ['large_tests'],
+                       'run_gdb_call_from_gdb_test')
+
 # GDB treats multithreaded programs specially. Provide distinct nexe for
 # multithreaded tests to isolate multiple threads-specific issues.
 gdb_test_guest_thread = env.ComponentProgram(